Seasonal-use devices include recreational vehicles and seasonal equipment, such as lawn mowers, yard tractors, personal watercraft, boats, motorcycles, snowmobiles, construction and agricultural equipment. Seasonal-use devices utilize batteries as an electric power source to provide electric start and control power to the device. During operation of the seasonal-use device, the internal battery charging system maintains the charge on the battery.
Because these devices are only used seasonally, the battery is normally stored for a number of months, which results in self-discharging of the battery. Internally, the battery is undergoing a process called plate sulfation, which creates an insulating coating on the plates preventing subsequent full performance from the battery. Once plate sulfation has occurred, even if the battery is fully charged, it will no longer operate at optimum efficiency and full battery capacity.
The type of battery most commonly used in seasonal-use vehicles is a lead-acid battery. Typically, lead-acid batteries will self-discharge at an approximate rate of 1 percent per day, yielding a battery which is approximately 80 percent discharged after just six months. The discharge condition of the battery causes the battery's plates to sulfate, resulting in a shortened battery life. It has been found that batteries allowed to self-discharge for six month periods usually have a life of about two years or about 1/3 the normal life expectancy and then must be replaced.
Diesel engines are popular since diesel engines can extract up to 50 percent greater energy from the same cost of fuel as compared to gasoline engines. Due to the high compression ratios of the diesel engines, they require very large battery packs for starting. These large battery packs are very costly, making it important to extend the battery life as long as possible.
Known battery charging system devices and methods include such apparatus disclosed in U.S. Pat. No. 3,568,031 to Eberts (Vehicle Power Supply for Battery Charging and Load Supply); U.S. Pat. No. 3,870,855 to Edlund et al. (Electric Heating and Battery Charging System for Motor Vehicle); U.S. Pat. No. 3,898,547 to Poole (Electric Vehicle Charger Shut-Off Interlock System); U.S. Pat. No. 5,017,856 to Johnson, Jr. (Battery Charging System); and U.S. Pat. No. 5,272,431 to Nee (Automatic Power Connector for Recharging Electric Vehicles).
U.S. Pat. No. 4,935,688 to Mystry et al. suggest that over time, the common lead-acid battery cell corrodes at the positive cell electrode due to the oxidizing conditions resulting from the repeated application of charging current to the cell. Mystry et al. '688 suggests minimizing the oxidization of the plates of electrolytic battery cells during flow charge by the application of a small additional current.
Other known mechanisms include "Off-Season Automatic Battery Maintainers" which suggest a wall-mount mechanism for maintaining full charge in a battery during long storage periods. The battery maintainer is wall mounted and plugs into a 120 volt outlet. Battery clamps are provided for coupling the maintainer to the vehicle battery. The battery maintainer provides a 1/2 amp to 1 amp charge as needed to the battery.
The disadvantage of present off-the-shelf battery maintainers is that they are not application specific. They have a preset maintenance current, which may result in maintaining small motorcycle batteries at far too high a current level, thereby destroying the motorcycle battery in a single off season. Likewise, the same battery maintainer may be unable to maintain large battery packs found in large agricultural tractors, resulting in discharge and battery sulfation. Further, no monitoring and control is built into the battery maintainers to prevent the above-stated problems from occurring.
Due to the high replacement cost of batteries and the environmental sensitivity to lead-based and other types of batteries, it is desirable to extend the life of these batteries. It is desirable to have an apparatus for providing a seasonal-use battery with a small amount of current equal to the battery's self-discharge current during storage, extending the battery life and preventing battery sulfation. Further, it is desirable to provide a battery life extender and control apparatus which is integrated into the existing battery charging system of the seasonal-use device, including the seasonal-use device control and display system, and which is application specific.